Imagewind displays in real time images that people post on Twitter using tools like Twitpic.

After submitting an update to the application, Roger Peters, the developer, received a note from Microsoft this week asking him to filter the content. "While the images shown are dynamic, per your app's disclaimer, a portion of the images' content is too graphic for the app to be permissible in Marketplace. In order to be permissible, there would need to be a content filter before surfacing images since users are not querying a specific type of image and are rather pushed to them," according to the note signed by the Windows Phone Marketplace Policy team.

"Given this, we ask that you unpublish your app within one business day until you are able to modify your application to comply with the certification guidelines," the note said.

Filtering the images isn't possible, Peters said. "Since Imagewind is entirely based on live unfiltered images from Twitter, there is no chance of me ever being able to comply with the policy team's request short of hiring a team to monitor and filter images 24/7. This rejection draws the line in the sand for what is and isn't allowed on Windows Phone, and it paints a distinct difference between what is allowed in the iPhone app store and the WP7 marketplace," he wrote in a blog post about the matter on Wednesday.

The incident points to the challenges mobile platform providers face when deciding how to best manage applications. Google is on one end of the spectrum, allowing any application in its store but reserving the right to later remove apps that violate its policies. That strategy has come under criticism because, as recently occurred, it can allow harmful apps in the store. Google recently reportedly pulled around 50 apps that were found to contain malware.